Field of the Invention
The present invention relates to a control method of a low voltage DC-DC converter for a hybrid vehicle that improves efficiency of a low voltage converter by varying application of output voltage of the low voltage converter based on drive modes and driving conditions of a hybrid vehicle.
Description of the Related Art
In general, a hybrid electric vehicle refers to a vehicle in which power sources are configured by an engine and a drive motor driven by power of a battery, and which promotes enhancement of fuel consumption with the assisting power of the motor driven by voltage of the battery when the vehicle is started or accelerated by combining the power sources to a front wheel.
In an electric vehicle, a controller configured to operate the vehicle includes a hybrid control unit (HCU) or a vehicle control unit (VCU). The HCU or VCU are configured to communicate with a motor control unit (MCU), which is a lower controller, by a predetermined type to adjust torque, speed, and generate torque amount of a motor as a power source, and communicate with an engine control unit (ECU), configured to adjust an engine generating power required for generating power as the assisted power source, to perform a relay control for engine starting and a failure diagnosis.
In addition, the HCU is configured to communicate with a battery management system (BMS) configured to manage the battery by detecting temperature, voltage, current, state of charge (SOC), and so on, of the battery to adjust torque and speed of the motor based on conditions of SOC, and communicate with a transmission control unit (TCU) configured to adjust gear ratio based on a vehicle speed and a drive command of a driver to maintain a vehicle speed required by the driver. The communication between the HCU as the higher controller and the lower controllers is performed by a controller area network (CAN) bus to exchange information with each other and transmit/receive control signals.
Meanwhile, the electric vehicle includes a low voltage DC/DC converter (LDC), this is, DC-DC converter configured to convert electric power of a high voltage battery to direct current (DC). The LDC is configured to convert DC to alternating current (AC), increase or decrease voltage using a coil, a trance, a capacitance, and so on, and then, generate DC to supply electricity that corresponds to voltage used in each electric field load.
For controlling the low voltage converter (LDC), many technologies have been developed. For example, a technology in the related art involves a method for improving output efficiency by turning off the LDC as a voltage drop device when high output is required in a vehicle. However, this technology merely controls on/off of the low voltage converter based on a vehicle condition, and does not adjust output voltage of the low voltage converter when the low voltage converter is on to improve efficiency of the low voltage converter.
The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art.